gpio: moxart: make explicitly non-modular

The Kconfig currently controlling compilation of this code is:

drivers/gpio/Kconfig:config GPIO_MOXART
drivers/gpio/Kconfig:   bool "MOXART GPIO support"

...meaning that it currently is not being built as a module by anyone.

Lets remove the couple traces of modular references so that when reading
the driver there is no doubt it is builtin-only.

Since module_platform_driver() uses the same init level priority as
builtin_platform_driver() the init ordering remains unchanged with
this commit.

We also delete the MODULE_LICENSE tag etc. since all that information
is already contained at the top of the file in the comments.

We don't replace module.h with init.h since the file already has that.

Cc: Jonas Jensen <jonas.jensen@gmail.com>
Cc: Alexandre Courbot <gnurou@gmail.com>
Cc: linux-gpio@vger.kernel.org
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>